Add global_cache_tracker stability tests.

This adds some tests to ensure that the database used in the global
cache tracker stays compatible across versions. These tests work by
using rustup to run both the current cargo and the stable cargo, and
verifying that when switching versions, everything works as expected.

Author: ehuss

.github/workflows/main.yml

@@ -156,6 +156,10 @@ jobs:
     - uses: actions/checkout@v4
     - name: Dump Environment
       run: ci/dump-environment.sh
+    # Some tests require stable. Make sure it is set to the most recent stable
+    # so that we can predictably handle updates if necessary (and not randomly
+    # when GitHub updates its image).
+    - run: rustup update --no-self-update stable
     - run: rustup update --no-self-update ${{ matrix.rust }} && rustup default ${{ matrix.rust }}
     - run: rustup target add ${{ matrix.other }}
     - run: rustup component add rustc-dev llvm-tools-preview rust-docs

tests/testsuite/global_cache_tracker.rs

@@ -1863,3 +1863,152 @@ fn clean_gc_quiet_is_quiet() {
         )
         .run();
 }
+
+#[cargo_test(requires_rustup_stable)]
+fn compatible_with_older_cargo() {
+    // Ensures that db stays backwards compatible across versions.
+
+    // T-4 months: Current version, build the database.
+    Package::new("old", "1.0.0").publish();
+    Package::new("middle", "1.0.0").publish();
+    Package::new("new", "1.0.0").publish();
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+                [package]
+                name = "foo"
+                version = "0.1.0"
+
+                [dependencies]
+                old = "1.0"
+                middle = "1.0"
+                new = "1.0"
+            "#,
+        )
+        .file("src/lib.rs", "")
+        .build();
+    // Populate the last-use data.
+    p.cargo("check -Zgc")
+        .masquerade_as_nightly_cargo(&["gc"])
+        .env("__CARGO_TEST_LAST_USE_NOW", months_ago_unix(4))
+        .run();
+    assert_eq!(
+        get_registry_names("src"),
+        ["middle-1.0.0", "new-1.0.0", "old-1.0.0"]
+    );
+    assert_eq!(
+        get_registry_names("cache"),
+        ["middle-1.0.0.crate", "new-1.0.0.crate", "old-1.0.0.crate"]
+    );
+
+    // T-2 months: Stable version, make sure it reads and deletes old src.
+    p.change_file(
+        "Cargo.toml",
+        r#"
+            [package]
+            name = "foo"
+            version = "0.1.0"
+
+            [dependencies]
+            new = "1.0"
+            middle = "1.0"
+        "#,
+    );
+    p.process("cargo")
+        .args(&["+stable", "check", "-Zgc"])
+        .masquerade_as_nightly_cargo(&["gc"])
+        .env("__CARGO_TEST_LAST_USE_NOW", months_ago_unix(2))
+        // Necessary since `process` removes rustup.
+        .env("PATH", std::env::var_os("PATH").unwrap())
+        .run();
+    assert_eq!(get_registry_names("src"), ["middle-1.0.0", "new-1.0.0"]);
+    assert_eq!(
+        get_registry_names("cache"),
+        ["middle-1.0.0.crate", "new-1.0.0.crate", "old-1.0.0.crate"]
+    );
+
+    // T-0 months: Current version, make sure it can read data from stable,
+    // deletes old crate and middle src.
+    p.change_file(
+        "Cargo.toml",
+        r#"
+            [package]
+            name = "foo"
+            version = "0.1.0"
+
+            [dependencies]
+            new = "1.0"
+        "#,
+    );
+    p.cargo("check -Zgc")
+        .masquerade_as_nightly_cargo(&["gc"])
+        .run();
+    assert_eq!(get_registry_names("src"), ["new-1.0.0"]);
+    assert_eq!(
+        get_registry_names("cache"),
+        ["middle-1.0.0.crate", "new-1.0.0.crate"]
+    );
+}
+
+#[cargo_test(requires_rustup_stable)]
+fn forward_compatible() {
+    // Checks that db created in an older version can be read in a newer version.
+    Package::new("bar", "1.0.0").publish();
+    let git_project = git::new("from_git", |p| {
+        p.file("Cargo.toml", &basic_manifest("from_git", "1.0.0"))
+            .file("src/lib.rs", "")
+    });
+
+    let p = project()
+        .file(
+            "Cargo.toml",
+            &format!(
+                r#"
+                    [package]
+                    name = "foo"
+
+                    [dependencies]
+                    bar = "1.0.0"
+                    from_git = {{ git = '{}' }}
+                "#,
+                git_project.url()
+            ),
+        )
+        .file("src/lib.rs", "")
+        .build();
+
+    p.process("cargo")
+        .args(&["+stable", "check", "-Zgc"])
+        .masquerade_as_nightly_cargo(&["gc"])
+        // Necessary since `process` removes rustup.
+        .env("PATH", std::env::var_os("PATH").unwrap())
+        .run();
+
+    let config = GlobalContextBuilder::new().unstable_flag("gc").build();
+    let lock = config
+        .acquire_package_cache_lock(CacheLockMode::MutateExclusive)
+        .unwrap();
+    let tracker = GlobalCacheTracker::new(&config).unwrap();
+    // Don't want to check the actual index name here, since although the
+    // names are semi-stable, they might change over long periods of time.
+    let indexes = tracker.registry_index_all().unwrap();
+    assert_eq!(indexes.len(), 1);
+    let crates = tracker.registry_crate_all().unwrap();
+    let names: Vec<_> = crates
+        .iter()
+        .map(|(krate, _timestamp)| krate.crate_filename)
+        .collect();
+    assert_eq!(names, &["bar-1.0.0.crate"]);
+    let srcs = tracker.registry_src_all().unwrap();
+    let names: Vec<_> = srcs
+        .iter()
+        .map(|(src, _timestamp)| src.package_dir)
+        .collect();
+    assert_eq!(names, &["bar-1.0.0"]);
+    let dbs: Vec<_> = tracker.git_db_all().unwrap();
+    assert_eq!(dbs.len(), 1);
+    let cos: Vec<_> = tracker.git_checkout_all().unwrap();
+    assert_eq!(cos.len(), 1);
+    drop(lock);
+}